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Archive for August, 2008

This Week in HTML 5 – Episode 1

Wednesday, August 6th, 2008

Welcome to a new semi-regular column, "This Week in HTML 5," where I'll try to summarize the major activity in the ongoing standards process in the WHATWG and W3C HTML Working Group.

The biggest news is the birth of the Web Workers draft specification. Quoting the spec, "This specification defines an API that allows Web application authors to spawn background workers running scripts in parallel to their main page. This allows for thread-like operation with message-passing as the coordination mechanism." This is the standardization of the API that Google Gears pioneered last year. See also: initial Workers thread, announcement of new spec, response to Workers feedback.

Also notable this week: even more additions to the Requirements for providing text to act as an alternative for images. 4 new cases were added:

  1. A link containing nothing but an image
  2. A group of images that form a single larger image
  3. An image not intended for the user (such as a "web bug" tracking image)
  4. Text that has been rendered to a graphic for typographical effect

Additionally, the spec now tries to define what authors should do if they know they have an image but don't know what it is. Quoting again from the spec:

If the src attribute is set and the alt attribute is set to a string whose first character is a U+007B LEFT CURLY BRACKET character ({) and whose last character is a U+007D RIGHT CURLY BRACKET character (}), the image is a key part of the content, and there is no textual equivalent of the image available. The string consisting of all the characters between the first and the last character of the value of the alt attribute gives the kind of image (e.g. photo, diagram, user-uploaded image). If that value is the empty string (i.e. the attribute is just "{}"), then even the kind of image being shown is not known.

  • If the image is available, the element represents the image specified by the src attribute.
  • If the image is not available or if the user agent is not configured to display the image, then the user agent should display some sort of indicator that the image is not being rendered, and, if possible, provide to the user the information regarding the kind of image that is (as derived from the alt attribute).

See also: revision 1972, revision 1976, revision 1978, revision 1979, Images and alternate text.

Other interesting changes this week:

Tune in next week for another exciting episode of "This Week in HTML 5."

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